The invention relates to an absorbent article intended for female users, such as a sanitary napkin or an incontinence protector, having such a form and size that it can principally be accommodated in the crotch part of a pair of underpants and having a longitudinal direction, a transverse direction and a thickness direction, wherein the article displays a liquid-permeable surface, and a liquid-impermeable surface, and also an absorbent core consisting of at least one absorbent body arranged between the two surfaces, and wherein a raised portion extending in the longitudinal direction is arranged at the liquid-permeable surface of the article.
A common problem associated with absorbent articles of the type intended here is leakage of body fluid out beyond the longitudinal side edges of the article. Such leakage is naturally extremely undesirable since it involves a risk of soiling the clothes of the user. Due to the rather inconsiderable extension of the article even in the longitudinal direction, it is, moreover, not unusual for liquid to leak out forward or backwards beyond the end edges of the article.
A common reason for edge leakage is that the absorbent article is deformed during use when the article is compressed between the thighs of the user. This leads to pleating in both the absorbent core of the article and in its cover material. Such pleating leads to channels being formed in an uncontrolled manner on the surface of the article, in which channel body fluid can run out beyond the side edge. Moreover, the compression of the article results in a reduction in the surface available for liquid acquisition, leading to a significant risk of body fluid ending up beside the article.
A further problem in connection with the previously known absorbent articles is that the side edges of the article, under the influence of the physical forces which arise when the user moves, are at risk of being folded in over the liquid-permeable surface of the article. Such inward folding also leads to a drastic reduction in the surface available for liquid acquisition as only a narrow liquid-permeable area remains between the inwardly folded side edges.
One way of reducing the risk of edge leakage caused by deformation of the article during use is to provide the article with a preformed raised portion, which during use is intended to lie against the genitalia of the user. In this way, excreted body fluid can be collected as soon as it leaves the body of the user and can be immediately absorbed into the article without running out over its surface.
However, a problem connected with absorbent articles on which a raised portion has been arranged is that the surface which the body fluid meets initially is strictly limited. As a result, during heavy flows of liquid it can occur that all the liquid cannot be immediately absorbed into the raised portion. It is not uncommon for liquid to accumulate between the body of the user and the raised portion. When the user stands up or moves in another way, a gap often occurs between the raised portion and the body of the user. If a large volume of unabsorbed liquid has been enclosed between the body of the user and the surface of the article, this liquid can then flow out through the gap. Such sudden flows of liquid are extremely undesirable as the user perceives them as being uncomfortable and also because they considerably increase the risk of leakage.
Thus, there remains a need for a leakproof absorbent article which works well even for large flows of liquid.
An article produced according to the invention, of the type stated in the introduction, is principally characterised in that the raised portion presents spacing elements which, during use of the article, create channels for liquid flow between the raised portion and the body of a user.
The spacing elements can be preformed before use or they can be made in such a way that they do not appear until after wetting.
One way of producing spacing elements which are activated by wetting is by forming a hump with raised portions and thereafter compressing the hump so that it obtains an essentially smooth surface. When the hump is wetted and absorbs liquid, the compressed raised portions will rise up again and form spacing elements on the surface of the hump. Suitable materials for achieving the desired effect are cellulose fluff pulp with high critical bulk, for example chemical thermomechanical cellulose fluff pulp (CTMP), absorbent foam material and other materials that maintain compression before wetting. The compressed structure can be bound with a water-soluble binding agent in order to maintain the compression before wetting.
Providing the raised portion of the article with spacing elements means that the raised portion will not seal against the body of the user. This eliminates the risk of liquid that has not had time to be absorbed by the raised portion being enclosed between the raised portion and the genitalia of the user. Instead, the liquid can run into the channels that are formed between the spacing elements and be absorbed by the side portions of the raised portion or in absorption material arranged at the base of the raised portion.
The spacing elements can be in the form of raised ridges, sunken channels or trenches or of a plurality of projection projecting from the raised portion. These projections can have any suitable form but, for reasons of comfort, should present a rounded surface towards the user of the article. If the spacing elements are in the form of ridges or channels, these should preferably extend principally in the transverse direction of the article. Accordingly, a raised portion can present both raised ridges and sunken channels, or both ridges and projections, etc.
The spacing elements can be formed integrally with the raised portion or they can consist of strips, bands or the like of absorbent or non-absorbent material which has been applied to the raised portion. The spacing elements can be part of a forming element which gives form stability to the raised portion.
It is an advantage if the raised portion is shape stable in both wet and dry conditions, since it is thus possible in each situation to predict the form of the raised portion. Being shape stable implies that the raised portion during normal use will remain essentially unaffected and will not be deformed when it is subjected to pressure and shearing forces arising during used. Furthermore, the shape of the raised portion should not be appreciably altered during absorption of body fluid. An absorbent article with a raised portion which resists deformation when subjected to pressure during use is described in PCT/SE97/01886. Further, absorbent materials that have essentially the same volume in wet and dry conditions are described in PCT/SE97/01883.
Another way to achieve a shape stable raised portion is when the raised portion comprises a forming element. Such a forming element advantageously comprises a rigid plastic material.
According to one embodiment of the invention, raised edge barriers are arranged along the side edges of the article.
According to another embodiment, a camouflage layer is arranged between the liquid-permeable cover layer and the spacing elements on the raised portion in order to conceal the spacing elements. Such a camouflage layer can be a very porous fibre layer which does not hinder the flow of liquid in the channels between the spacing elements. Alternatively, the camouflage layer can be formed of material which collapses when wetted, whereby the raised portion of the article during and after use has a relief structure that is observable from the surface.
Examples of materials which can be used to camouflage the spacing elements are fibres of viscose, cotton, hydrophilicised polypropylene, or mixtures thereof.
To prevent the raised portion from causing discomfort in the form of chafing or pressure during use, but nevertheless to provide good body contact so that excreted body fluid can be collected as soon as it leaves the body of the user, it is essential that the raised portion is given an anatomically correct form. A hard, shape stable hump, which essentially is not affected by the forces occurring during use, should not, accordingly, be so high that it presses against the body of the user and thus causes discomfort during use. Further, it is necessary to ensure that the raised portion does not chafe the sensitive soft parts in the crotch of the user. If has been shown that a raised portion which at its highest part projects at least 5 mm, but not more than 20 mm, from the surface of the article fulfills the requirements of both good body contact and high user comfort.
Correspondingly, a shape stable hump should be relatively narrow, suitably between 2 mm and 25 mm at the base and preferably between 12 mm and 16 mm. The hump is suitably formed with a principally triangular cross section and, accordingly, it is broader at the base than at the top. As the hump is relatively narrow, it can, without discomfort to the user, project in somewhat between the labia of the user. It is an advantage if the hump parts the labia somewhat as this facilitates the transfer of liquid from the user to the article.
The raised portion should have such a form at its rear part that it lies in close contact against the body of the user in the area behind the vaginal opening. Body fluid is thus prevented from running backwards in the furrow between the buttocks of the user and leaking out of the article. Such backward leakage is especially troublesome when the user is lying down. In a corresponding manner, the front part of the raised portion should connect against the body shape of the user in the area in front of the vaginal opening.
In order to connect against the anatomy of the user, the raised portion should be highest at that part of the article which is intended to lie against the vaginal opening of the user. From the highest part, the height should gradually decrease in a direction towards the end portions of the article. The raised portion should extend backwards from the highest part between 5 mm and 40 mm and preferably between 10 mm and 30 mm. In front of the highest part, the raised portion should have a length of between 30 mm and 90 mm, preferably between 55 mm and 80 mm. The raised portion suitably has a total length which is between 40 mm and 140 mm in the longitudinal direction of the article and preferably between 70 mm and 120 mm.
A raised edge barrier can advantageously be arranged on both sides of the central raised portion. The edge barriers increase the leakage security of the article by serving as seals against the groin of the user. Raised edge barriers can be produced in a number of different ways. Examples of commonly occurring side barriers are elastic side edges, foam rubber strips, wadding or the like. Edge barriers can either be purely physical barriers or can prevent the passage of liquid by absorbing body fluid.